Since the dawn of the computer age hardware components have been malfunctioning and software has been attempting to deal with it. Storage devices such as hard-disk and solid-state drives have a limited life and are the focus of much work to detect, correct, and preemptively replace those components when defective. The problem is that with all this effort is software frequently gets it wrong with false-failure rates often over 50%. The term No Trouble Found (NTF) is used in the electronics industry to describe components that have been returned for replacement but operate properly when tested.
The general problem is that the software that removes faulty components from services relies on a static model, i.e. so many errors in so many minutes from a particular device results in its indictment as the culprit. The reality is that the behavior of components, the OS software that monitors them, and the procedures that qualify them are all in a constant state of change. There has been a lack of efficient ways to determine the faulty disks from those that have been falsely-failed.